Improving the production rate of high-value nutraceutical compounds, such as astaxanthin and polyunsaturated fatty acids (PUFAs), is important for the commercialization of Haematococcus pluvialis biorefineries. Here, the effects of a phytohormone, strigolactone analog rac-GR24, on cell growth and astaxanthin and fatty acid biosynthesis in H. pluvialis were investigated. Four concentrations (2, 4, 6, and 8 µM) of rac-GR24 were initially added during 30 days of photoautotrophic cultivation. The addition of rac-GR24 improved cell number density and chlorophyll concentration in H. pluvialis cultures compared to the control; the optimal concentration was 8 µM. Despite a slightly reduced astaxanthin content of 30-d-old cyst cells, the astaxanthin production (26.1 ± 1.7 mg/L) improved by 21% compared to the rac-GR24-free control (21.6 ± 1.5 mg/L), owing to improved biomass production. Notably, at the highest dosage of 8 µM rac-GR24, the total fatty acid content of the treated H. pluvialis cells (899.8 pg/cell) was higher than that of the untreated cells (762.5 pg/cell), resulting in a significant increase in the total fatty acid production (361.6 ± 48.0 mg/L; 61% improvement over the control). The ratio of PUFAs, such as linoleic (C18:2) and linolenic (C18:3) acids, among total fatty acids was high (41.5–44.6% w/w) regardless of the rac-GR24 dose.

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Phycocyanin is a blue pigment that is found in cyanobacteria such as Spirulina platensis. Its ability to provide stable and non-toxic blue color makes its market value is so high that it reaches USD 112.3 million in 2018. However, the cultivation of S. platensis to produce phycocyanin can only be carried out by large-scale industry, due to high operating costs of synthetic medium such as Zarrouk. We considered the use of Anaerobically Digested Dairy Manure Wastewater (ADDMW) as an alternative for growth medium to produce phycocyanin from S. platensis. A laboratory-scale study was conducted to determine the optimum composition of the medium containing ADDMW and NaHCO3 as a carbon source for S. platensis. We found that the ADDMW medium combined with 16.8 g/L NaHCO3 and 25 g/L NaCl resulted the highest productivity of phycocyanin among the other variations. Industrial-scale economic analysis of this integrated cultivation method showed its economic feasibility using 10 years lifetime analysis. Highest GPM (gross profit margin) obtained is 12.40 with IRR (internal rate of return) 23% which give 3.13 years of payback period. Futher study is needed on technical aspect and actual implementation of industrial scale design.

Chromium in the form of hexavalent chromium (VI) has been used in some industry including leather tanning industry. The chemical has been known to be harmful to  living organism. Therefore, it is important to treat wastewater from leather tanning industry before being discharged to the environment. The aim of this study is to examine physiological strategies of Eichhornia crassipes  to tolerate Cr6+ accumulation in its tissue, compared to sensitive species Pistia stratiotes. The variations of Cr6+ concentrations were 0, 40, 80 and 120 ppm. Some parameters including catalase, APX, chlorophyll and proline enzymes in both plants were measured. The biomass yield of plant in Cr6+ stress was negative (-0.732 to -1.84 g/week) which indicated both E. crassipes and P. stratiotes  reduced their growth. The higher the concentration of Cr6+, the lower the chlorophyll contents in the leaves. The lowest of chlorophyll content was in 120 ppm (0.15 mg/g in P. stratiotes  and 0.12 mg/g in E. crassipes). The highest of CAT activity in E. crassipes was 109% in 40 ppm Cr6+, while in P. stratiotes  was 76% in 120 ppm. Proline content in both E. crassipes and P. stratiotes  were not different significantly. In general, E. crassipes plants have the ability to adapt to Cr6+ stress which is better when compared to P. stratiotes  plants which was severely damaged when grown in high Cr6+ concentration. Both plants can remediate waste fairly well (% elimination 62-68%) during the exposure period of 14 days.

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